Glass-front office warm by afternoon: condenser heat trapped in service recess

A Downtown Core office cooled acceptably in the morning but became warm after lunch. The pattern followed glass-facade heat and long runtime. Before treating it as a gas problem, the outdoor heat path had to be checked.

By Team Snowflake | Updated 28 Jul 2026

Case summary

Mitsubishi Electric Cassette5 years oldOfficeDowntown Core, Singapore

Concern: Facilities team expected a gas leak because the office cooled in the morning but failed by afternoon.
Found: Condenser recycling hot air inside a tight service recess
Key check: Checked the condenser discharge path during afternoon office load
Result: After the recess was cleared and the hot-air path improved, afternoon temperature stayed more stable. The team had a building-access item to manage instead of a blind gas top-up. Future complaints can now be checked against afternoon load and recess airflow first.

What we were told

The office was comfortable in the morning, then drifted warm by mid-afternoon. Staff had already cleaned the return filter. The facilities contact suspected a slow gas leak because the unit still ran but could not hold temperature.

What we checked

The time pattern pointed away from a constant fault and toward load or heat rejection. We checked the indoor cassette first, then followed the system to the condenser recess. The unit was mounted in a tight service pocket where discharged hot air had limited escape, especially when neighbouring condensers were also running.

Indoor airflow was acceptable and the cassette was not iced over.
The warm complaint was strongest after several hours of office runtime.
The condenser sat inside a narrow service recess with poor hot-air escape.
Nearby units were adding heat to the same pocket.

What we found

The condenser was recycling hot air in the service recess. In the morning, the load was low enough that the system appeared normal. By afternoon, solar heat through the glass and heat from neighbouring outdoor units raised the temperature in the recess. The condenser could still run, but it was trying to cool itself with already-warm air. That reduced heat rejection and made the office temperature drift. The fault was therefore placement and airflow, not an immediate gas top-up case.

What fixed it

We explained the airflow limitation and recommended clearing the recess, opening the discharge path where building rules allowed, and reviewing louver direction with management if the symptom returned. We did not quote parts because the checks did not support a failed component. The useful fix was to reduce heat recycling and then monitor afternoon performance under a normal occupied workday. If the office still warmed up after airflow changes, deeper checks would be justified.

Outcome

After the recess was cleared and the hot-air path improved, afternoon temperature stayed more stable. The team had a building-access item to manage instead of a blind gas top-up. Future complaints can now be checked against afternoon load and recess airflow first.

What this case teaches us

CBD cooling loss can be an outdoor airflow problem

Offices with glass frontage and long runtime put more load on the condenser after lunch. The timing matters.
A service recess can trap the same hot air the condenser is trying to reject. That makes the indoor space warm without proving a gas leak.
Ask for the outdoor hot-air escape path to be checked before approving gas work, especially in dense commercial buildings.

Questions this case answers

Office cools fine in the morning and turns warm after lunch. What changes?

Afternoon is when the outdoor side runs out of room to dump heat. This Downtown Core office sat behind glass frontage, and the condenser was tucked in a narrow service pocket with poor hot-air escape. By mid-afternoon that pocket was full of warm air from this unit and its neighbours, so the system was cooling itself with heat it had just rejected.

Does an office that cannot hold temperature mean a slow gas leak?

Not when the pattern follows the clock. A leak drags cooling down steadily rather than tracking the working day. Here the cassette was not iced over, indoor airflow was acceptable, and the complaint peaked only after several hours of runtime. The limitation sat in the condenser's discharge path, so no parts were quoted.

What can be done if the condenser sits in a cramped service recess?

Free up the discharge path as far as the building allows. Clearing the recess, opening the escape route and reviewing louver direction with management were the useful moves here, followed by watching afternoon temperature through a normal occupied day. If the office still drifted warm after that, deeper checks would have been justified.

Do neighbouring outdoor units affect my own aircon?

In a shared pocket, yes. Several condensers venting into the same tight space raise the air temperature every one of them has to draw from, so each works harder than it would alone. That was part of what tipped this office over by mid-afternoon, and it is a building-access item rather than an equipment fault.

Ready to get started?

Tell us what’s going on. Symptoms, setup, photos, anything we should know. We’ll assess and come back with the right next step.

WhatsApp us